This invention relates to an apparatus for gasification of a solid carbonaceous material, particularly to a gasification apparatus utilizing a molten metal bath, in which the heat required for gasifying the solid carbonaceous material is supplied through said molten metal bath. More particularly, this invention relates to a gasification apparatus utilizing a molten metal bath, from which the slag formed during gasification can be discharged in a continuous manner without tilting the furnace, in which gasification of a solid carbonaceous material such as coal, coke, etc. (hereunder sometimes collectively referred to as "coal") is carried out under pressure. The gasification apparatus utilizing a molten metal bath is hereinafter sometimes called a "molten metal coal gasification apparatus" or a "molten iron coal gasification apparatus" for convenience.
Many types of coal gasification processes and apparatuses using a molten metal bath have been proposed in the past.
One type is found in U.S. Pat. Nos. 4,388,084 and 4,389,246 in which pulverized coal, oxygen, and other auxiliary gasification agents are blown through a top-blowing lance onto the surface of a high temperature molten metal bath prepared in a furnace. This is hereinafter called a "top-blowing" system for convenience.
There are two types of furnaces used therefor; one is a tilting-type furnace similar to an oxygen converter used for steel making, i.e. a vertical type furnace; and the other one is a fixed type box furnace, i.e. a horizontal type furnace.
The gasification furnace of the top-blowing system has the following disadvantages:
(i) Since the slag formed is built-up within the furnace after a long-run operation, resulting in a decrease in gasification efficiency, a suitable means has to be provided to discharge the slag from the furnace. In case of the tilting-type furnace, the furnace is tilted for slag discharge, and during the discharge of slag the operation of gasification furnace has to be stopped. This means that it is impossible to continue the gasification for a long period of time.
(ii) Since the amount of slag increases during gasification, powdery coal to be blown into the molten metal bath is mostly caught by slag after the slag is built-up excessively and the coal thus caught is exhausted together with the gas from the molten metal bath before it is thoroughly subjected to gasification. This increases the flying loss of powdery coal, i.e. the loss of pulverized coal entrained by the product gas before it reaches the molten metal bath. In addition, this also increases the slag loss of coal, i.e. the loss of coal which is caught by the slag. Thus, the gasification efficiency as well as the heat content of the product gas decrease.
U.S. Pat. Nos. 3,533,739 and 3,526,478 propose another type of system of coal gasification in which pulverized coal is blown into a molten metal bath through a bottom-blowing nozzle provided in the bottom of the furnace. This system is hereinafter called a "bottom-blowing" system.
However, according to the system of the above U.S. patents, the lifetime of the bottom-blowing nozzle is very short. In addition, a decrease in gasification efficiency and heat content is inevitable with this bottom-blowing system due to an inevitable build-up of slag during gasification, although they are not so severely reduced as in the case of the top-blowing system. This is one of the difficulties which must be overcome in order to achieve a continuous and long-run gasification operation.